Grains are often substituted for forage in ruminant diets to increase feed intake, diet fermentability, and animal growth rate. However, greater dietary starch concentration can lead to digestive disorders, such as ruminal acidosis and reduce performance (Owens et al., 1998). Adding non-forage fibre source, such as sugar beet pulp (SBP), to low-forage diets might reduce the negative effects of increased starch fermentation without increasing the filling effect of the diet to the same extent as forage fibre. So, substituting SBP for barley grain in a diet with moderately low forage content should alter ruminal fermentation and might increase mean or minimum ruminal pH. Thus, the objective of this study was to evaluate the effect of the substitution of barley grain with SBP on ruminal pH and ammonia nitrogen (NH3-N) concentration in Holstein steers.